Hermetically sealed pump-motor assembly cooling system for absorptionrefrigeration apparatus



P. EDBERG 3,295,335

-MOTOR ASSEMBLY COOLING SYSTEM FOR 2 Sheets-Sheet 1 Jan. 3, 1967 HERMETICALLY SEALED PUMP ABSORPTION-REFRIGERATION APPARATUS Filed OCt. 21, 1963 \%@M c \N. WW

Jan. 3, 1967 P. EDBERG 3,295,335

HERMETICALLY SEALED PUMP-MOTOR ASSEMBLY COOLING SYSTEM FOR ABSORPTION-REFRIGERATION APPARATUS Filed Oct. 21. 1963 2 Sheets-Sheet 2 52 Per [diary United States Patent 3,295,335 HERMETECALLY dEAlLED PUMlP MQTOR ASSEM- BLY COULING SYSTEM FOR AESGRPTHGN- REFRIGERATEON APPARATUS Per Edberg, Spring Garden Township, York County, Pa, assignor to Borg-Warner Corporation, Qhicago, ML, a corporation of lltinois Filed Qct. 21, 1963, Ser. No. 317,661 '7 Claims. (Cl. 62-476) This invention relates to an improved pump motor cooling system and more particularly to a system for cooling hermetically sealed pump and motor assemblies associated with an absorption refrigeration apparatus.

Absorption refrigeration systems conventionally employ a plurality of pumping means for circulating the refrigerant and the absorber soiution, commonly a saline solution such as lithium bromide. In a typical apparatus of the aforementioned class, pumping means are provided for passing the dilute solution (a solution less concentrated in lithium bromide) from the absorber to the generator where the refrigerant (water) is boiled off, the solution being concentrated thereby. Additional pumping means are required for re-circulating refrigerant through the evaporator and for circulating the concentrated soluvtion, or an intermediate strength mixture of dilute and concentrated solutions, through the absorber.

In order to increase the reliability of these units, hermetically sealed pump-motor assemblies are often used instead of the more conventional types. Since the absorption system operates under absolute pressures substantially lower than atmospheric, a pump seal failure on an ordinary pump would permit air and sealant water to enter the system. Leakage of air and water will adversely affeet the machine perfor nance and air in particular will retard the absorption effect and cause crystallization of solution and create severe corrosion and corrosion products.

Hermetically sealed pump notor assemblies present a number of special problems, particularly in providing a suitable method for removing the heat generated within the pump-motor assembly. In the designs which are cooled by an internally circulating fluid, the cooling medium passes into intimate contact with the moving parts of the pump motor, i.e., through the bearings and between the rotor and the stator. It is absolutely necessary that all precautions be taken to maintain a cooling fluid free from dirt, grit, and other foreign material to prevent such material from interfering with the operation of the pump motor. It should be understood that the term hermetically sealed pump-motor unit is meant to embrace any combined pumping means and prime mover for driving said pumping means both of which are sealed insofar as practical within an encapsulating casing or shell.

It is therefore a principal object of the invention to provide an improved pump-motor assembly cooling system for an absorption refrigeration apparatus.

Another object of the invention is to insure that the pump motor cooling fiuid is kept clean and free from foreign material which could cause damage to the pump motor.

Other and more particular objects and advantages will be apparent from the following detailed description taken in conjunction with the appended drawings wherein:

FIGURE 1 is a schematic illustration of a cooling system associated with an absorption refrigeration apparatus; and

FIGURE 2 is a cross-sectional view of the evaporator pump and the motor cooling fluid heat exchanger.

In a preferred embodiment of the invention, a liquid coolant system is provided for cooling the pump-motor assemblies so that said assemblies are cooled indirectly by 3,295,335 Fatentetl Jan. 3, 19%? a stream of cold, liquid refrigerant from the absorption system. The cooling fluid is constantly recirculated through the various pumps and through the heat exchanger so that the cooling fluid never comes in direct contact with the evaporator or with any of the internal portions of the absorption-refrigeration apparatus. One known prior art system taps off a small quantity of refrigerant and passes it directly through the hermetically sealed pump motor units incorporated in the absorption unit. This arrangement, however, is not fully satisfactory because corrosion and scale in the evaporator-absorber shell could enter the cooling water lines and eventually get into the pump motors, fouling the bearings and possibly rendering the motor inoperative. With the close tolerances in motors of this type, a small quantity of foreign material could cause considerable damage. Reliance on filters and other such means for purging the coolant of impurities have not proven to be satisfactory.

The absorption system is of a conventional design and comprises a generator, a condenser, an evaporator, and an absorber connected to provide a closed circuit, refrigeration system. Referring now to FIGURE 1, it will be noted that a shell llii is provided having heat exchangers l1 and 12 received therein. The upper heat exchanger 11 is provided with a pan 13 located immediately underneath said heat exchanger which combines therewith to form condenser 15. The lower heat exchanger 12 cooperates with the lower portion of shell lit to form a generator 16.

The evaporator and absorber are disposed within a separate shell 26. Heat exchanger Zll, commonly referred to as the chilled water line, combines with a pan 2?. to form an evaporator 23. Heat exchanger 2s cooperates with the lower portion of shell 20 to provide an absorber 27. Although the complete refrigeration circuit is not shown in the drawing, the operation of this type of unit will be familiar to those skilled in the art.

A plurality of pumping means are provided in the system for circulating absorber solution and refrigerant, said pumping means including an absorber pump 3t an evaporator or refrigerant pump 31, and a generator pump 32. The absorber pump 30 continuously circulates an intermediate strength mixture of concentrated and dilute solutions over the absorber heat exchanger 26 to absorb the water vapor evaporated in the evaporator. The refrigerant pump Tdl recirculatcs liquid refrigerant over the evaporator or chilled water coil 21, said refrigerant being collected in the pan 22 and directed to a spray header (not shown) located above said chilled water coil. The generator pump 32 circulates dilute solution, i.e., solution weak in water vapor absorbing power, to the generator 16, where heat supplied by heat exchanger 12 boils off the refrigerant and concentrates the solution. The refrigerant condenses on the condenser coil 12, collects in pan 13 and is supplied through conduit means 25 to the evaporator in the lower shell. A heat exchanger (not shown) is usually provided to pass the solutions leaving and entering the generator in heat exchange relation.

Each of the pumps comprises a combined pump and motor assembly which is hermetically sealed to prevent air and other non-condensibles from mentoring the system. Since the heat generated within the combined pump and motor assembly cannot be effectively dissipated through the encapsulating shell, auxiliary means for cooling the pumps have to be provided. Ordinarily, a liquid cooling fluid is circulated internally of the hermetically sealed casing to effect cooling.

It is an important aspect of the present invention that the system employs a captive pump motor cooling medium which is continuously circulated through a heat exchanger 34 in indirect heat exchange relation with cold, liquid refri erant tapped off from the main evaporator or refrigerant pump dischange. The cold, liquid refrigerant is circulated through the heat exchanger and returned to the evaporator pump inlet. Make-up cooling fluid is supplied by providing a small, auxiliary collection pan 35 in the condenser underneath the condenser coil which is connected to heat exchanger 34 through conduit means 37. It will be understood that the refrigerant evaporated in the generator condenses on the condensing coils and a major portion thereof is supplied to the evaporator. The collection pan 35 is kept filled with the condensed refrigerant and maintains a level in the pan to supply contaminant-free cooling fluid while the system is in operation. Any excess condensate flows over into the main collection pan 13. The auxiliary collection pan 35 is preferably located above the heat exchanger 34 thereby providing a column of fluid to maintain a static pressure head on the fluid within the heat exchanger.

Heat exchanger 34 may be of any conventional design but in a preferred embodiment, the unit comprises a shell 36 having a coiled tube 38 arranged axially of said shell. The motor cooling fluid passes on the shell side of the heat exchanger, externally of tube 38, and is delivered through line 4-0 to a header 41 for distribution to the pump-motor assemblies 31, 32, and 33. A magnetic strainer 44 is located at the connection of line 40 to header 41 as an additional safety feature.

Individual cooling fluid inlet lines 45, 46, and 47 are connected to header 41 to supply each of said pumpmotor assemblies. Cooling fluid return lines 50, 51, and 52 from the pump-motor assemblies interconnect with a return header 53 and conduit means 54 to the shell side of heat exchanger 34.

The cold, liquid refrigerant for chilling the motor cooling fluid is circulated through the tube side of heat exchanger 34 by tapping off from the discharge side of the refrigerant pump 31 through conduit means 55 to heat exchanger 34. A return line 56 interconnects the tube 38 with the inlet side of refrigerant pump 31.

Referring now to FIGURE 2, which is a more detailed cross-sectional view of the refrigerant pump and the cooling fluid heat exchanger, it will be noted that the refrigerant pump-motor assembly includes a motor section 63 and a pump section 62. Motor section 651) is enclosed by a housing 63 in which is positioned a wound stator 64 and a rotor as connected to ,a shaft 68 driving the pump impeller 70. The rotor shaft 68 is journalled within front and rear bearing elements '72, 74 respectively and engages a thrust bearing 76. On the back side of the rotor, the shaft carries a cooling fluid pumping element or centrifugal impeller 75 adjacent the rear bearing 74.

The heat exchanger 34, as mentioned previously, includes a shell 36, and a coiled tube 38 extending longitudinally thereof. The return fluid from the pump-motor assemblies is directed through an annular space 80 defined between the shell 36 and a cylindrical baflle element 82 in which the coil 33 is positioned. In a preferred embodiment, a float switch 84 is provided, said switch being actuated by a float element 85 and adapted to shut down the system in the event there is insuflicient cooling fluid present within the heat exchanger to supply the pump-motor assemblies.

After the system is initially filled with cooling fluid '(through filler pipe 79 and its associated valve 81) and :in operation, make-up fluid is automatically supplied to the coolant system, as required, through the vertically extending conduit means 29 connected to the auxiliary collection pan 35 underneath the condenser coil. FIGURE 2 illustrates the motor cooling fluid passing only through the refrigerant pump motor assembly, it should While tween the rotor and the stator. The fluid then passes through the front rotor shaft bearing 72 and through fluid passage means 77 formed in the motor casing to return conduit means 51. The return fluid from the absorber and generator pump motors is similarly inter-connected with the return header 53.

Various control arrangements, either manually or automatically actuated, may also be provided in the system. For example, as shown in FIGURE 2, valves 83, 84 are connected into the refrigerant tap-off and return lines 55 and 56 respectively. If, for some reason, the apparatus is not able to produce refrigeration, these valves may be closed and water from an external source may be hooked up to the two pipe Couplings indicated at 85, 86. Another valve 88 shown in FIGURE 1 is provided in line 37 to permit shutting off of the supply of make-up coolant fluid during prolonged shut down periods. If such means were not provided, refrigerant in line 37 and within the heat exchanger 34 might evaporate and cause the float switch to interrupt the control system and thereby prevent starting of the machine until chamber 36 were again manually refilled.

While this invention has been described in connection With a certain specific embodiment thereof, it is to be understood that this is by way of illustration and not by way of limitation; and the scope of this invention is defined solely by the appended claims which should be construed as broadly as the prior art will permit.

What is claimed is:

1. In an absorption refrigeration system of the type including an absorber, a generator, a condenser, an evaporator, and a plurality of hermetically sealed pump-motor assemblies for circulating solution and refrigerant through the system, the combination of:

a heat exchanger;

means for withdrawing a continuous stream of cold refrigerant flowing in the evaporator circuit of said absorption system;

means for circulating a coolant for said pump-motor assemblies through said heat exchanger in heat exchange relation with said cold refrigerant; means for circulating said coolant through each of said pump motor assemblies internally thereof in a closed circuit and back to said heat exchanger; and

means for collecting condensed refrigerant in said condenser to provide make-up cooling fluid.

2. A cooling system adapted to remove internally generated heat from a plurality of hermetically sealed pumpmotor assemblies associated with an absorption refrigeration apparatus comprising:

a heat exchanger including tube means and a shell enclosing said tube means;

means for circulating cold liquid refrigerant from said absorption refrigeration system through said heat exchanger tube means;

means for circulating a coolant for said hermetically sealed pump motor assemblies through said heat exchanger, said coolant circulating on the outside of said tube means; and

means associated with each of said pump motor assemblies for circulating said coolant internally through said pump motor assemblies in a closed circuit back to said heat exchanger.

3. Apparatusas defined in claim 2 including means for supplying additional coolant to said cooling system as required, said means including a pan for collecting clean refrigerant in the condenser section of said absorption refrigeration apparatus.

4. In an absorption refrigeration system of the type including an absorber, a generator, an evaporator, and a condenser connected in a closed circuit, the combination comprising:

a plurality of pumping means including a generator pump for circulating absorber solution from said absorber to said generator, an absorber pump for circulating absorber solution through said absorber, an evaporator pump for circulating liquid refrigerant through said evaporator;

each of said pumping means comprising a hermetically sealed pump and motor assembly;

a heat exchanger;

means for circulating a stream of cold refrigerant through said exchanger;

means for circulating a pump motor cooling fluid through said heat exchanger in indirect heat exchange relation with said stream of cold refrigerant and through each of said pumping means; and

said pump motor cooling fluid circulating in a closed circuit from said heat exchanger through each of said pump motors.

5. Apparatus as defined in claim 4 including means for supplying make-up motor cooling fluid to said coolant system including means for collecting refrigerant in said condenser.

6. In an absorption refrigeration apparatus of the type including a condenser and hermetically sealed absorber, generator, and evaporator pump-motor assemblies for circulating solution and refregerant through said system, the combination comprising: heat exchange means for passing liquid coolant in indirect heat exchange relation With a stream of cold refrigerant; means for circulating said liquid coolant in a closed circuit through each of said pump-motor assemblies and back to said heat exchange means; a receptacle for collecting clean refrigerant in said condenser; and means for automatically supplying said refrigerant as makeup coolant from said receptacle to said closed circuit.

7. In an absorption refrigeration system of the type including an absorber, a generator, an evaporator, and a condenser connected in a closed circuit, the combination comprising: a plurality of pumping means including a generator pump for circulating absorber solution from said absorber to said generator, an absorber pump for circulating absorber solution through said absorber, an evaporator pump for circulating liquid refrigerant through said evaporator, each of said pumping means including a hermetically sealed pump and motor assembly; means for circulating a fluid coolant in a closed circuit through each of said pump and motor assemblies; a receptacle for collecting clean, condensed refrigerant in said condenser; and means for supplying, on demand, the condensed refrigerant in said recptacle to the coolant circuit for use as a makeup coolant.

References Cited by the Examiner UNITED STATES PATENTS 5/1961 Edberg et al 62-505 X 8/1964 Aronson 62141 

1. IN AN ABSORPTION REFIGERATION SYSTEM OF THE TYPE INCLUDING AN ABSORBER, A GENERATOR, A CONDENSER, AN EVAPORATOR, AND A PLURALITY OF HERMETICALLY SEALED PUMP-MOTOR ASSEMBLIES FOR CIRCULATING SOLUTION AND REFRIGERANT THROUGH THE SYSTEM, THE COMBINATION OF: A HEAT EXCHANGER; MEANS FOR WITHDRAWING A CONTINUOUS STREAM OF COLD REFRIGERANT FLOWING IN THE EVAPORATOR CIRCUIT OF SAID ABSORPTION SYSTEM; MEANS FOR CIRCULATING A COOLANT FOR SAID PUMP-MOTOR ASSEMBLIES THROUGH SAID HEAT EXCHANGER IN HEAT EXCHANGE RELATION WITH SAID COLD REFRIGERANT; MEANS FOR CIRCULATING SAID COOLANT THROUGH EACH OF SAID PUMP MOTOR ASSEMBLIES INTERNALLY THEREOF IN A CLOSED CIRCUIT AND BACK TO SAID HEAT EXCHANGER; AND MEANS FOR COLLECTING CONDENSED REFRIGERANT IN SAID CONDENSER TO PROVIDE MAKE-UP COOLING FLUID. 